Friction welding apparatus

ABSTRACT

In a known method of friction welding two workpieces together, one workpiece is reciprocated relative to the other while the workpieces are pressed together. When sufficient frictional heat has been generated, relative movement is caused to cease and the workpieces become welded. Apparatus for carrying out that method comprises power-driven reciprocatory means which carries the reciprocating workpiece. To balance the reciprocatory means there are counterweights which move in the opposite direction to the reciprocatory means. Each counterweight is constrained by guide means to move along a rectilinear path. Each counterweight is coupled to the reciprocatory means by reversing means, which comprises a pivoted rocker, first linking means and second linking means. Each linking means may be constituted by a flexible blade which is anchored in a non-pivotal manner to the reciprocatory means, the rocker or the counterweight, as the case may be.

This is a continuation-in-part of application Ser. No. 07/340,723 filedMar. 22, 1989, now U.S. Pat. No. 4,905,883.

This invention relates to friction welding apparatus.

In one method of generating heat for friction welding two workpiecestogether, a first one of the workpieces is caused to reciprocate whilein contact with the other, or second, of the workpieces, the first andsecond workpieces being pressed together so that frictional heat isgenerated between them.

When sufficient heat has been generated to enable welding to beeffected, relative reciprocatory movement between the workpieces iscaused to cease and the workpieces are pressed together so that theybecome welded together. It is usual for the second workpiece to remainstationary, or substantially stationary, during the generation offrictional heat. In the description of the present invention thatfollows, it will be assumed that the second workpiece does indeed remainstationary, or substantially so; nevertheless it is to be understoodthat in making use of the invention the second workpiece may also becaused to reciprocate, or may be caused to move in some other manner,relative to the first workpiece during the generation of frictionalheat.

Difficulties can arise in designing mechanism for causing reciprocationof the first workpiece. The difficulties can be particularly severe whenthe workpieces to be welded together are made of metal and have to beraised to a relatively high temperature before welding can be effected.Difficulties may arise, for example, from the fact that the firstworkpiece must be caused to reciprocate rapidly, typical rates ofreciprocation being between 1000 and 6000 reciprocations per minute;each reciprocation is considered to be a complete cycle of movement, sothat if, for example, the reciprocation is of simple harmonic form, eachreciprocation is a full 360° movement. Difficulties may also arise fromthe fact that the frictional resistance forces that must be overcome arenot only relatively high, being as great as 50 or 100 tonnes or evengreater, but also vary during the frictional generation of heat, andfrom the fact that the relative movement between the workpieces must bestopped rapidly when the required temperature has been reached andusually the workpieces must then be located in predetermined relativepositions before they are welded together.

One aim of the present invention is to enable at least some of thosedifficulties to be reduced or overcome.

From a first aspect the present invention consists in apparatus for usein friction welding comprising apparatus for use in friction welding afirst workpiece to a second workpiece, comprising driving means,reciprocatory means which is driven by said driving means and isoperative in use to carry the first workpiece and to cause reciprocationof that first workpiece relative to the second workpiece such as willlead to the generation, between the workpieces, of frictional heat forwelding, and balancing means comprising at least one counterweight andassociated reversing means connected between the reciprocatory means andthe counterweight in such a manner that movement of the reciprocatorymeans in either direction causes simultaneous movement of thecounterweight in the opposite direction, the apparatus beingcharacterised in that said reversing means comprises a pivoted rocker,first linking means connected at one end to the reciprocatory means andat the other to the rocker, and second linking means connected at oneend to the counterweight and at the other end to the rocker.

Preferably there is guide means operative to guide said counterweightfor reciprocatory movement along a rectilinear path.

Said rocker is preferably pivoted about an axis midway betweenconnections for said first and second linking means. Preferably thefirst and second linking means are mutually parallel and extend on thesame side of the rocker. The first linking means is preferably equal inlength to the second linking means.

Preferably each of the linking means is flexible and each end of each ofthe linking means is connected to said reciprocatory means, said rockeror said counterweight, as the case may be. Each flexible linking meansis preferably constituted by a flexible blade. This is preferably arectilinear blade which is of uniform cross-section over at least mostof its length. End portions of the flexible blade may be ofprogressively increasing thickness and thus of progressively increasingstiffness.

The use of flexible linking means connected by non-pivotal anchoragesobviates the need to provide pivotal connections. This can simplify thedesign of the apparatus quite considerably as it will be appreciatedthat if, for example, rigid linking means were used to interconnect thereciprocatory means and the pivoted rocker and to interconnect thepivoted rocker and the counterweight, each of the connections being apivotal connection, then each of the pivotal connections would, in use,be subjected to forces that would be relatively large and rapidlychanging in direction, while subjected to rotational movement to andfro, through only relatively small angles. Such pivotal connectionswould doubtless require relatively large bearing surfaces and would bedifficult to lubricate satisfactorily. In some circumstances,nevertheless, those difficulties may not be insuperable, but itsgenerally preferred to use flexible coupling means.

It is to be understood that throughout this specification, including theclaims, the term non-pivotal anchorage, when used to described theattachment of a flexible component of the apparatus to some othercomponent of the apparatus, is intended to denote a form of attachmentsuch as to permit no relative movement between the components at thepoint of attachment; moreover the term anchored is used to includeconstructions in which a flexible component is formed integrally withanother component.

One embodiment, of the present invention will now be described in moredetail, by way of example, with reference to the accompanying drawings,in which:

FIG. 1 is a schematic view illustrating the principles of apparatus foruse in friction welding and embodying the present invention,

FIG. 2 is a side elevation of apparatus for use in friction welding andembodying the principles illustrated schematically in FIG. 1, certainparts being omitted for clarity,

FIG. 3 is an end elevation of the apparatus, to a larger scale, asviewed from the right of FIG. 2,

FIG. 4 is a plan view, to a larger scale, of the apparatus shown in FIG.2,

FIG. 5 is a section, to a larger scale, along the line 5--5 of FIG. 2,

FIG. 6 is a section, to a larger scale, along the line 6--6 of FIG. 2,

FIG. 7 is a scrap view to a further enlarged scale, of a detail of FIG.6, and

FIG. 8 is a section through an end part of a flexible blade,illustrating its anchorage to another part of the apparatus.

FIG. 1 is a schematic view illustrating apparatus for use in frictionwelding and embodying the present invention. Only part of the apparatusis shown, but the part that is omitted, to the right of the Figure, issimilar to the part shown, the apparatus being symmetrical about thecentre-line 1. For clarity of description, components shown to the leftof the centre-line 1 will be designated by reference numerals, whilethose to the right of the centre-line will be designated by the samereference numerals to each of which is added a prime (').

The apparatus includes a rigid, stationary frame, not shown in FIG. 1.The apparatus also includes a rotatable drive member 2. An eccentric 3on the drive member 2 carries a follower 4. A reciprocable outputelement 5 which constitutes a reciprocatory means of the kind referredto above is coupled to the follower 4 by flexible connecting means 6.The element 5 is mounted in guides (not shown in FIG. 1) so that it isconstrained to move to and fro along a rectilinear path. The flexibleconnecting means 6 comprises two pairs of flexible metal blades 7. Thecomponents 2, 3 and 4 together constitute driving means. A central partof the element 5 is coupled to one end part 8 of integrating means,illustrated schematically here in the form of a simple rigid beam 9,which constitutes a linking body, by means of a flexible blade 10constituting flexible coupling means. A central part of the beam 9 iscoupled to one end portion of a rigid reciprocable ram 11 by means of aflexible main blade 12 constituting main flexing means, anchored to theram and the beam. The ram 11 is so mounted that it can reciprocate in alongitudinal direction but cannot move in any other direction. To thisend a central part of the ram 11, which also constitutes a reciprocatorymeans of the kind referred to above is connected to the central part ofa flexible diaphragm 13, of which the outer edges are anchored to thestationary frame of the apparatus.

Balancing means is provided for the reciprocating components of theapparatus. Illustrated in FIG. 1 are balancing means for thereciprocable output element 5, the beam 9 and the ram 11. End portionsof the reciprocable element 5 are coupled to end portions of a pair ofrockers 14 and 15 by means of flexible blades 16 and 17, whichconstitute first linking means and are respectively anchored to theelement and rockers. Flexible blades 18 and 19, which constitute secondlinking means, are anchored respectively to the other end portions ofthe rockers 14 and 15 are also anchored to respective cylindricalcounterweights 20 and 21 which are mounted in guides (not shown inFIG. 1) which constrain them to move only along rectilinear pathsparallel with their longitudinal axes. The rockers 14 and 15 are mountedat their centres on pivot pins 22 and 23 respectively which are mountedin blocks (not shown in FIG. 1) fixed to the frame of the apparatus.That end portion of the ram 11 to which the main blade 12 is connectedis also coupled to end portions of a pair of rockers 24 and 24' by meansof flexible blades 25 and 25', which also constitute first linkingmeans, anchored to the ram and the rockers. The rocker 24 is mounted atits centre on a pivot pin 26 mounted in a block fixed to the frame ofthe apparatus, and the other end portion of the rocker is coupled to acylindrical counterweight 27 by means of a flexible blade 28, which alsoconstitutes second linking means, anchored to the rocker and thecounterweight. Like the counterweights 20 and 21, the counterweight 27is constrained to move along a rectilinear path parallel with itslongitudinal axis.

The drive members 2 and 2' can be rotated by a common motor (not shownin FIG. 1). Adjustment means (also not shown in FIG. 1) is provided toenable the relative phase of the drive members, and consequently of theeccentrics 3 and 3' to be adjusted.

In use the drive members 2 and 2' are rotated at the same speed. Theeccentric 3 causes the follower 4 to perform orbital motion, that is tofollow a circular path but without bodily rotation. That orbital motioncauses reciprocatory motion of the output element 5, relative lateralmovement between the follower 4 and the element 5 being accommodated byflexure of the blades 7 of the flexible connecting means 6. Thereciprocatory motion of the element 5 is transmitted to the end part 8of the beam 9 through the intermediary of the coupling blade 10. Whenthe eccentrics 3 and 3' are exactly in phase with each other, the blades10 and 10' reciprocate in unison, thus causing the beam 9 to reciprocatebodily without any rocking movement. When the eccentrics 3 and 3' areexactly 180° out of phase with each other, however, the blades 10 and10' reciprocate out of phase with each other with the result that thebeam 9 rocks back and forth about its centre without moving bodily. Theresultant slight angular movement of the end parts 8 and 8' of the beam9 relative to the output elements 5 and 5' is accommodated by flexure ofthe blades 10 and 10'. When the eccentrics 3 and 3' are in any otherout-of-phase relationship, the resultant movement of the beam combinesboth bodily movement and rocking movement. If the adjustment means isoperated to cause the eccentrics to shift from a state in which theyrotate in unison to a state in which they are 180° out of phase witheach other, the amplitude of bodily movement of the central part of thebeam is progressively reduced from a maximum value to zero. Moreover,the final position of the central part of the beam is half way betweenthe end points of its travel when it was reciprocating bodily to andfro. Bodily movement of the central part of the beam 9 is transmitted tothe ram 11 by the main blade 12, any rocking movement of the beam beingaccommodated by flexure of the main blade.

Reciprocating movement of the connecting means 6, element 5 and end part8 of the beam 9 is balanced by reciprocatory movement of thecounterweights 20 and 21, the counterweights always moving in theopposite direction from the connecting means, element and end part. Thisis brought about by rocking movement of the rockers 14 and 15 abouttheir pivot pins 22 and 23. Relative angular movements that occurbetween the rockers and the element 5 and the counterweights 20 and 21are accommodated by flexure of the blades 16, 17, 18 and 19.Reciprocatory movement of the remaining, central part of the beam 9 andof the ram 11 is similarly balanced by the movement of thecounterweights 27 and 27'. As the rockers 24 and 24' rock about theirpivot pins 26 and 26', relative angular movement between the rockers andthe ram and the counterweights 27 and 27' are accommodated by flexure ofthe blades 25 and 27. The effect of the balancing means in use is toensure that the frame as a whole experiences little or no resultantreciprocatory force tending to rock it to and fro. The angular rockingmovement of the beam 9 is not balanced, it is only the translational,reciprocatory component of movement of the beam that is balanced. Forthis purpose the beam is treated as if it were in three independantparts: two end parts 8 and 8' and the remaining central part. Asexplained above, the end parts are balanced by the counterweights 20,21, 20' and 21' while the central part is counterbalanced by thecounterweights 27 and 27'. This compromise solution to the problem ofbalancing the beam avoids the need for independant counterweights forthe beam and is found to be entirely adequate.

The apparatus illustrated in FIG. 1 is intended to be used in thefollowing manner. A first one of two workpieces to be welded together(not shown) is secured to that end of the ram 11 further from the mainblade 12, while the second of those workpieces is pressed laterallyagainst it and is restrained from reciprocating with the firstworkpiece. The motor is operated to rotate the drive members 2 and 2'and the adjustment means is adjusted so that the first workpiece iscaused to reciprocate. When sufficient frictional heat has beengenerated between the workpieces to enable the workpieces to be weldedtogether, the adjustment means is adjusted to bring the eccentrics 3 and3' out of phase so that the first workpiece ceases to reciprocate. Theworkpieces continue to be pressed together and become welded to eachother.

It is to be understood that the mass of the first workpiece can bebalanced by suitable selection or adjustment of the mass of thecounterweights 27 and 27'.

It will also be appreciated that while welding is being effected thereis no need for the drive members 2 and 2' to cease rotation.

A practical embodiment of apparatus in accordance with the presentinvention is illustrated in FIGS. 2 to 7. As will become apparent, thelay-out of the apparatus is different from that illustratedschematically in FIG. 1, but in all major respects the components of thepractical embodiment are the same as those in the schematic apparatus,they are interconnected in the same manner and operate in the samemanner. The apparatus is relatively complex in construction, and a fewminor simplifications have been made in the drawings in order toillustrate the invention clearly. For example, a casing 29 for much ofthe apparatus is partially omitted from some views.

The apparatus will be described as being in an orientation in which itis primarily intended to be used. Nevertheless, as explained in moredetail below, the apparatus may be used in a different orientation.

The apparatus is intended for use in welding together metal workpieces.It is intended that in use the force exerted by the ram should notexceed 15 tonnes, and that the ram should perform about 4500reciprocations per minute, with a maximum stroke of 6 mm.

The apparatus comprises a rigid, fabricated metal base 30. Pillars 31 onthe base support a thick metal base plate 32 which extends horizontally.Eight tubular metal pillars 33 on the base plate 32 support a thickmetal top plate 34, parallel with the base plate 32. The pillars 33 arewelded to the base plate and the top plate 34, but to avoid the weldbeing subjected to tension in use, axially extending tie bolts, intension, act between the pillars and the plates so that the welds arealways in compression. In use the rigid framework thus formed housescomponents of less than one tonne in total mass, but in use may besubjected to reciprocating forces of approaching 70 tonnes. Anadditional eight tubular metal pillars 35 on the base plate 32 support athick metal welder plate 36 which is spaced a short distance above thetop plate 34. As there is no direct connection between the top plate andthe welder plate, reciprocating forces to which the top plate aresubjected in use are not transmitted to the welder plate.

An electric motor 37 is mounted on a stand 38 on the base 30. Thisdrives a main shaft 39 which constitutes the drive member 2 (or firstrotatable input member) referred to above. A sleeve 40, constituting thedrive member 2' (or second rotatable input member), is rotatably mountedon a part of the shaft 39 spaced from the motor. The angularrelationship between the shaft 39 and the sleeve 40 is controlled byadjustment means 41. This is shown in section in FIG. 5.

A helically splined gear 42 is secured to the end of the sleeve 40 bymeans of an attachment device 43 housed in an annular groove, the innerwall of which is defined by the sleeve and the outer wall of which isdefined by the gear. The attachment device 43 is shown to a larger scalein FIG. 7. A ring 44 of tapered cross-section engages the inner wall ofthe groove and a ring 45 of similar cross-section engages the outerwall. Wedging rings 46 and 47 engage the inclined faces of the rings 44and 45. Screws are disposed at uniform intervals around the rings. Theshank of each screw, such as the screw 48, passes through a hole in thewedging ring 47 and engages a threaded hole in the ring 46. When thescrews are tightened, the rings 44 and 45 are resiliently deformed andare brought into tight abutment with the sleeve 40 and gear 42respectively, thereby securing them together. In use, when varying loadsare applied to the sleeve and the gear, the loading on the components ofthe attachment device varies but does not normally fall to zero, withthe result that there is no tendency for the device to become loose orto be damaged.

Thrust bearings 50 act between the gear 42 and an integral, axialextension 51 of a second helically splined gear 52. Attachment devices53 and 54, similar to the device 43, secure the gear 52 to the mainshaft 39. A cup-shaped extension 55 secured to the gear 52 houses thrustbearings 56 that act between the extension and a composite projection 57which is secured to one end of a piston rod 58 constituting part of anhydraulic piston-and-cylinder unit. As can be seen in FIG. 2, the pistonrod 58 extends through an hydraulic cylinder 59 of the unit and issecured to a bracket 60 attached to the base 30 of the apparatus. Whenthe hydraulic unit is operated, the cylinder 59 moves axially on thepiston rod 58. An extension 61 attached to the cylinder 59 carriesthrust bearings 62 which act between the extension and an annular member63 attached to one end of a composite sleeve 64 which extends axiallypast both the gear 52 and the gear 42. Rings 65 and 66 with internalhelical teeth are fixed inside the sleeve 64 and engage the splines ofthe gears 42 and 52 respectively. The splines on those gears are ofopposite hands.

In use, when the adjustment means is in the state illustrated, rotationof the main shaft 39 by the motor 37 causes rotation of the gear 52which in turn causes rotation of the gear 42 and sleeve 40 through theintermediary of the sleeve 64 and internally-toothed rings 65 and 66.When the adjustment means is then operated to move the cylinder 59 toits opposite end position, the sleeve 64 is pulled to the right, asviewed in FIGS. 2 and 5. As the toothed rings 65 and 66 move along thesplines of the gears 42 and 52, the gears rotate relative to each otherin opposite directions, as do the sleeve 40 and main shaft 39 to whichthe gears are secured. The total relative rotation is 180°.

During the period the adjustment means is in operation, the main shaft39 and sleeve 40 rotate a plurality of times. During that rotation, eachof them is subjected to varying torques from the eccentrics. The reasonfor this is as follows. When the phase-difference between the eccentrics3 and 3' is at any value between 0° and 180° the first workpiece isreciprocating and experiences considerable frictional resistance, whichmay, for example, be of the order of 15 tonnes. During part of eachrotation of the main shaft 39 and sleeve 40, one of the followers 4 and4' is rising while the other is moving downwards. The rate of upwardmovement of the rising follower is not normally the same as the downwardmovement of the other follower so that there is a resultant movement,either upwards or downwards, of the ram 11. Taking the case of the ramrising, this is a consequence of the rising follower moving more rapidlythan the descending follower. When this occurs, the rising follower willexert a force on the beam 9 which will tend to urge the descendingfollower downwards, its descent in fact being controlled by itsassociated eccentric. Therefore the eccentric will at that timeexperience a torque tending to rotate it forwards instead of the torquethat opposes rotation and that is more usually experienced.

The varying torques experienced by the eccentrics act in directions suchas to urge the sleeve 40 to rotate relatively to the main shaft 39alternately in one rotational sense and in the other. Reversal of thetorque in that manner would tend to rattle the toothed rings 65 and 66relative to the gears 42 and 52 and to cause damage. In order to preventthis phenomenon, brake means 67 is provided to operate continuouslybetween the sleeve and the main shaft. The resistance afforded by thebrake means during an adjustment period overrides the effect of thealternating torque applied by the eccentrics so that the resultant totaltorque, which is the sum of the torques applied by the followers and thetorque applied by the brake means, is always applied in a singledirection such as to resist relative rotation between the sleeve and themain shaft.

Details of the brake means 67 are shown in FIG. 6. An annular body 68 issecured to the main shaft 39 by an attachment device 69 similar to thedevice 43, and an annular body 70 is secured to the sleeve by a similarattachment device 71. Mutually abutting brake discs 72 and 73 aredisposed between the bodies 68 and 70. A dowel 74 anchors the disc 72against rotation relative to the body 68, and a dowel 75 anchors thedisc 73 against rotation relative to the body 70. Outer parts of thediscs lie between the body 70 and a backing ring 76 secured to the body70 by screws 77. A bearing ring 78 in the body 70 engages the disc 73and is urged towards it by groups of Belleville springs 79 bearing on itat intervals around it. The springs 79 abut associated screws 80 in thebody 70.

As shown in FIG. 2, the main shaft 39 is rotatably mounted in a pair ofaxially spaced bearing assemblies 81 secured by screw-and-nut assemblies82 to the base plate 32. The sleeve 40 is rotatably mounted in a pair ofaxially spaced bearing assemblies 83 secured by screw-and-nut assemblies84 to the base plate 32. The four bearing assemblies are all of similarconstruction; part of one of the assemblies 83 is shown in FIG. 6, whereinclined tapered rollers are shown as acting between a frusto-conicalface of a ring 85 keyed to the sleeve 40 and a frusto-conical face of aring 86 secured to a fixed component 87.

The main shaft 40 is formed with an eccentric portion between thebearing assemblies 83; this eccentric portion is the embodiment of theeccentric 3 described above with reference to FIG. 1. The main shaft 39is formed with a similar eccentric portion 3' between the bearingassemblies. The axes of the eccentrics are spaced 3 mm from the commonaxis of the main shaft and sleeve. The arrangement is such thatoperation of the adjustment means 41 adjusts the eccentrics from a statein which they are in phase with each other to a state in which they are180° out of phase. The eccentrics 3 and 3' rotate in followers 4 and 4'.As shown in FIG. 6, a bearing 88 with tapered rollers acts between theeccentric 3' and the follower 4'. A disc is keyed to the sleeve 40 oneach side of the eccentric 3', one of those discs, 89, being shown inFIG. 6. Similar discs are keyed to the main shaft 39, one on each sideof the eccentric 3. Each of the four discs carries a counterweight nearits periphery, that on disc 89 being shown at 90. The arrangement issuch that the centre of mass of each eccentric, with its associated pairof counterweights is located on the axis of rotation of the shaft 39 andsleeve 40.

Through holes 91 in the base plate. 32 accommodate parts of thefollowers and the associated connecting means 6 and 6'. As can be seenin FIG. 3, each pair of metal blades 7' of the connecting means 6' isformed from a single piece of metal. Each end portion of each blade isof progressively increasing thickness and merges into an associated endblock. The connecting means 6' are anchored to a reciprocable element 5'which is of the shape illustrated. The element 5' has a central web 92in the shape of a rectangle from which two adjacent corner portions havebeen removed. Stiffening flanges 93 extend along upper and lower edgesof the web, while a pair of parallel locating flanges 94 extendvertically between central parts of the flanges 93. Upper and lowerbearing blocks 95 (omitted from FIG. 3 but shown in FIG. 2) project intothe grooves between the locating flanges 94. The bearing blocks aremounted on cross-members 96 fixed to pillars 33 and constrain theelement 5 so that it can reciprocate vertically but can move in no othermanner. In FIG. 3 the rockers 14' and 15', blades 16', 17', 18' and 19',counterweights 20' and 21', and pivot pins 22' and 23' are clearlyshown. The pivot pins 22' and 23' extend through blocks 97 secured tothe top plate 34. The counterweights 20' and 21' extend through annularbearing rings 98, in fixed plates 99 secured to pillars 33, and canslide axially in those rings.

In FIG. 1, the blade 10 is shown as extending upwards from the element 5away from the eccentric 3. In the practical embodiment, however, theblade 10 extends downwards. Likewise the blade 10' extends downwardsfrom the element 5' towards the eccentric 3' and is disposed between thepairs of flexible blades 7. Moreover, in FIG. 1 the side blade 10, likeall the flexible blades, is shown as being flexible laterally, i.e. inthe plane of the Figure, whereas in the practical embodiment, as shownin FIGS. 2 and 3, the blade 10' is turned through 90° and is flexible indirections at right angles to the blades 7'. That end of the side blade10' further from the element 5' is formed integrally with an enlargedblock 100' which enters the adjacent hole 91 in the base plate 32.

The components driven by the eccentric 3 are similar to those describedabove as being driven by the eccentric 3' and will not be furtherdescribed. As before, components driven by the eccentric 3' are givenreference numerals to which primes are added.

The blocks 100 and 100' are connected to opposite end parts of the beam9, which in the practical embodiment of the invention, is constituted bya pair of rigid, parallel plates 101. As shown in FIG. 2, each plate isin the shape of a rectangle with two adjacent corners removed. The mainblade 12 extends between the plates 101 and is disposed half way betweenthe coupling blades 10. At its lower end the main blade 12 is formedintegrally with a block 102 (FIG. 2) end portions of which extendbeneath the plates 101 and are anchored to the plates. In use, when theeccentrics 3 and 3' are out of phase with each other, the beam 9 rocksto and fro. As the coupling blades 10 and 10' and the main blade 12 areall of the same length and are disposed parallel to one another, therocking movement of the beam results in the three blades all flexing inthe same manner. As a consequence of that, the upper ends of the threeblades remain in mutual alignment; for example, when the upper end ofone side blade rises and that of the other falls through the samedistance, the level of the upper end of the main blade 12 remainsunaltered in spite of the fact that the lower end of the main blade mayrise slightly as a consequence of the flexure of the blades.

When the beam 9 rocks as described above, and the main blade 12 flexes,the axis about which that rocking or tilting takes place extendshorizontally through the main blade at a level a little above the lowerend of the main blade. The exact location of the axis can best bedetermined by experiment. It is desirable that the axis about which thebeam rocks should pass through the centre of mass of the beam, and tothis end holes 103 are formed in the plates 101. Trunnions 104 co-axialwith the axis of rocking or tilting project outwards from the plates 101and are rotatable in blocks 105 slidable vertically between parallelguide plates 106 mounted on the base plate 32. This arrangementrestricts the movement of the beam and prevents it moving endwise, thatis to right or left viewed in FIG. 2, something that might otherwiseoccur with the flexure of the coupling blades 10 and 10' and main blade12.

At its upper end the main blade 12 terminates in an integral top plate107 which extends in a horizontal plane and is of rectangular shape. Thevertical edge face of the plate are machined and slide between bearingpads 108 adjustably mounted on pillars 33. The ram 11, which extendsvertically upwards from the top of the plate 107, is of H-shapedcross-section and has a horizontal closure plate at each of its upperends. The ram thus has a vertically extensive niche in each side. Theblades 25 and 25' are accommodated in those niches, their lower endsbeing anchored to closure plates at the lower end of the ram, thatclosure plate being anchored to the top plate 107 of the main blade. Theupper ends of the blades 25 and 25' are anchored to the inner ends ofthe rockers 24 and 24' respectively, which project into upper parts ofthe niches in the ram. The pivot pin 26 is axially aligned with thepivot pins 22 and 22', while the pivot pin 26' is axially aligned withthe pivot pins 23 and 23'. The counterweights 27 and 27' are constrainedso as to be movable only vertically, in the same way as counterweights20, 20', 21 and 21' are constrained.

An upper end portion of the ram is disposed in a central aperture in thetop plate 34. The upper end of the ram 11 is secured to the central partof the flexible diaphragm 13 which permits vertical reciprocation of theram but prevents horizontal movement thereof. Outer edge portions of thediaphragm are located in the top plate 34. As the ram, in use,reciprocates with a maximum stroke of 6 mm the movement can beaccommodated by resilient distortion of the diaphragm even though theouter edge portions thereof are anchored to the top plate. The diaphragmmay be a thin metal plate of circular outline. Alternatively it may be athin metal plate of cross-shaped configuration in which case it may beformed from a circular disc from which four areas have been removed,each of which is approximately in the shape of a quadrant.

A work carrier 109 secured to the top of the ram 11 extends verticallyupwards through a central aperture in the welder plate 36, aligned withthe central aperture in the top plate 34.

A backing member 110 is secured to one side of the work carrier 109.Flexible blades 111 extend one on each side of the backing member andare anchored at one end to the backing member and at the other end to arigid support structure 112 mounted on the welder plate 36. The cylinder113 of an hydraulic piston-cylinder unit 114 abuts the structure 112between the blades 111. The piston rod 115 of the unit is connected to acarriage 116 of H-shaped configuration in plan. Parallel side arms 117of the carriage carry longitudinally extending bearing plates 118 whichare engaged by bearing pads 119 adjustably mounted in supportingstructures 120 secured to the welder plate 36 one on each side of thecarriage. A second work carrier (not shown) is incorporated in thecarriage.

A lower part of the work carrier 109 is provided with a locator 121which includes a pair of tapered, wedge-shaped heads that project fromopposite sides of the carrier. Locating jaws 122 of complementary shapeto those heads are mounted on the inner ends of rods 123 which areaxially movable in bores in the welder plate 36. The outer end of eachrod is attached to the piston rod of an hydraulic piston-and-cylinderunit 124 of which the cylinder is secured to the welder plate.

The apparatus operates in the following manner. Metal workpieces to bewelded together are secured one to the work carrier 109 and the other tothe work carrier incorporated in the carriage 116. The two workpieceshave mutually abutting planar faces which are in a vertical plane normalto the axis of the piston-and-cylinder unit 114. The motor 37 is broughtinto operation (if not already operating) and the adjustment means 41 isadjusted to bring the eccentrics 3 and 3' into phase with each other.This causes the ram 11 and the first workpiece to reciprocate with amaximum stroke of 6 mm. The piston-and-cylinder unit 114 is operated tourge the second workpiece against the first workpiece. The reaction tothe force applied to the reciprocating first workpiece by the secondworkpiece is transmitted to the backing member 110 and thence throughtension in the flexible blades 111 to the support structure 112 againstwhich the cylinder 113 abuts. In this way the reaction is not applied tothe welder plate 36. Moreover the arrangement is preferably such thatcentral parts of the mutually abutting faces of the workpieces are inthe same horizontal plane as the mid-planes of the blades 111; thishelps to prevent those abutting faces being forced from the vertical.

When sufficient frictional heat has been generated between theworkpieces to enable the workpieces to be welded together, theadjustment means 41 is operated as rapidly as possible to bring theeccentrics 3 and 3' 180° out of phase with each other. This causes theamplitude of reciprocation of the ram and the first workpiece to bereduced to zero. Although the reciprocation of the ram has ceased, itsvertical position relative to the base plate 32 is likely to beindeterminate. This partly is a consequence of effects of any remainingcompression or tension of the components of the apparatus, and partly aconsequence of any remaining frictional forces acting between theworkpieces that are to be welded together. In order to locate the workcarrier 109 accurately relative to the welder plate 36, the units 124are operated. They cause the jaws 122 to engage the tapered heads of thelocator 121 and to bring the locator, with the work carrier, to apredetermined level relative to the welder plate.

Continued force is exerted by the unit 114, urging the workpiecestightly into contact, so that they components become welded together.After welding is completed the unit 114 is operated to retract itspiston rod 115 and withdraw the carriage 116 so that the weldedworkpieces can be removed. New components to be welded together can thenbe mounted in place and welding can be effected without the need to stopthe motor 37.

The operation of the apparatus can be modified, if desired, by adjustingthe adjustment means 41 in such a manner that during the frictionalgeneration of heat the eccentrics 3 and 3' not 180° out of phase but areat some lesser angle out of phase. The consequences of this are that anincreased force is transmitted to the ram, though the amplitude ofreciprocation is reduced. Alternatively the apparatus may be modified sothat the maximum extent to which the eccentrics are out of phase is lessthan 180°.

It is intended that the apparatus should primarily be operated when inthe orientation described and illustrated that is with the axis of themain shaft 39 horizontal and the direction of reciprocation of the ram11 vertical. The only disadvantage of this arrangement is that theapparatus is relatively tall (for example about 3.5 m) so that anoperator handling the workpieces cannot stand on the same floor-level asthe base 30. In an alternative orientation the apparatus is disposedwith the axis of the main shaft still horizontal but with the directionof reciprocation of the ram also horizontal. The base 30 is anchored tothe floor, while the top plate 34 and welder plate 36 are supported forhorizontal sliding movement on supports that are also anchored to thefloor.

Modifications of the apparatus are, of course, possible. For example,the reciprocable output element 5 may be anchored to one end of aflexible blade, or one end of an assembly of such blades, the other endof which is anchored to a fixed part of the apparatus, the bearingblocks 95 and associated parts then being omitted. In use the element isconstrained by the blade or blades to reciprocate along a predeterminedpath which is substantially rectilinear. The element 5' may be mountedin a similar manner.

In another modification, the reciprocable output elements 5 and 5' areomitted entirely, and the followers 4 and 4' are linked directly to endparts of the beam 9 or other linking body by coupling means eachcomprising one or more flexible blades. If the apparatus illustratedwere modified in this way, the beam 9 would have to be raised to thelevel of the elements 5 and 5' (now omitted) so that the whole apparatuswould then be increased in height.

In the apparatus described, the first workpiece is secured to the workcarrier 109 so as to reciprocate in unison with it. It may, however,sometimes be desirable to mount the first workpiece in such a mannerthat it is reciprocable along an arcuate or other non-rectilinear pathand to couple the workpiece to the work carrier by means of some form ofcoupling, preferably comprising flexible component or components.

It is to be understood that each of the components of the apparatus thatflexes when the apparatus is in use, such as the blades 7, 7', 10, 10',12, 16, 16', 17, 17', 18, 18', 25, 25', 28 and 28', is made from steel.The ends of each such component are anchored to other components so thatthere is no relative movement at the point of anchorage. The anchoragemay, at least in some cases be effected by integral formation so thatthe components are formed as a unitary whole. Alternatively thecomponents may be formed separately and secured together. Particularcare is usually necessary at these locations in order to ensure asatisfactory and robust anchorage. The main problem that tends to ariseat such location is that of fretting corrosion. If there is any relativemovement between the two components anchored together the repeatedmovement that occurs as the components are reciprocated in use canquickly lead to one or both of the components being damaged. It maysuffice merely to bolt the components together, spring metal dowelspreferably also being used to locate the components laterally. Anotherpossible arrangement is illustrated in FIG. 8. This is a section throughan end part of a flexible blade 125 with an enlarged end portion 126,and through an adjacent component 127 to which the blade is anchored.The blade 125 is provided with an integral extension 128 which projectsbeyond the enlarged end portion 126 and is aligned with the blade 125.The extension runs for the full width of the blade, as does the enlargedend portion. The extension 128 enters a groove formed in the component127, which is wider than the blade. The enlarged end portion 126 seatsfirmly against the component on either side of the groove. Tapped holesare formed in the end of the extension 128 at uniform intervals alongthe extension. Cap screws such as the screw 129 extend through holes inthe component that communicate with the bottom of the groove. The screwsenter the tapped holes in the extension. When the screws are tightenedup, the blade is firmly anchored to the component, and provided thecomponents are accurately manufactured, without play, fretting corrosionis avoided in use. It will be observed that sharp corners are avoidedwhere the extension 128 meets the enlarged portion of the blade.

I claim:
 1. Apparatus for use in friction welding a first workpiece to asecond workpiece, comprising driving means, reciprocatory means which isdriven by said driving means and is operative in use to carry the firstworkpiece and to cause reciprocation of that first workpiece relative tothe second workpiece such as will lead to the generation, between theworkpieces, of frictional heat for welding, and balancing meanscomprising at least one counterweight and associated reversing meansconnected between the reciprocatory means and the counterweight in sucha manner that movement of the reciprocatory means in either directioncauses simultaneous movement of the counterweight in the oppositedirection, the apparatus being characterised in that said reversingmeans comprises a pivoted rocker, first linking means connected at oneend to the reciprocatory means and at the other to the rocker, andsecond linking means connected at one end to the counterweight and atthe other end to the rocker, and wherein guide means is provided, saidguide means being operative to guide said counterweight forreciprocatory movement along a rectilinear path.
 2. Apparatus accordingto claim 1, characterised in that said rocker is pivoted about an axismidway between connections for said first and second linking means. 3.Apparatus according to claim 1, characterised in that the first andsecond linking means are mutually parallel and extend on the same sideof the rocker.
 4. Apparatus according to claim 1, characterised in thatthe first linking means is equal in length to the second linking means.5. Apparatus according to claim 1, characterised in that each of thelinking means is flexible and that each end of each of the linking meansis connected by a non-pivotal anchorage to said reciprocatory means,said rocker or said counterweight, as the case may be.
 6. Apparatusaccording to claim 6, characterised in that each flexible linking meansis constituted by a flexible blade.
 7. Apparatus for use in frictionwelding a first workpiece to a second workpiece, comprising drivingmeans, reciprocatory means which is driven by said driving means and isoperable in use to carry the first workpiece and to cause reciprocationof that first workpiece relative to the second workpiece such as willlead to the generation, between the workpieces, of frictional heat forwelding, and balancing means comprising at least one counterweight andassociated reversing means connected between the reciprocatory means andthe counterweight in such a manner that movement of the reciprocatorymeans in either direction causes simultaneous movement of thecounterweight in the opposite direction, the apparatus beingcharacterised in that said reversing means comprises a pivoted rocker,first linking means connected at one end to the reciprocatory means andat the other to the rocker, and second linking means connected at oneend to the counterweight and at the other end to the rocker, and whereineach of the linking means is flexible and each end of each of thelinking means is connected by a non-pivotal anchorage to saidreciprocatory means, said rocker or said counterweight, as the case maybe.
 8. Apparatus according to claim 7, characterised in that eachflexible linking means is constituted by a flexible blade.
 9. Apparatusaccording to claim 7, characterised in that there is guide meansoperative to guide said counterweight for reciprocatory movement along arectilinear path.
 10. Apparatus according to claim 7, characterised inthat said rocker is pivoted about an axis midway between connections forsaid first and second linking means.
 11. Apparatus according to claim 7,characterised in that the first and second linking means are mutuallyparallel and extend on the same side of the rocker.
 12. Apparatusaccording to claim 7, characterised in that the first linking means isequal in length to the second linking means.
 13. Apparatus for use infriction welding a first workpiece to a second workpiece, comprisingdriving means, reciprocatory means which is driven by said driving meansand is operative in use to reciprocate along a rectilinear axis and tocarry the first workpiece and to cause reciprocation of that firstworkpiece relative to the second workpiece such as will lead to thegeneration, between the workpieces, of frictional heat for welding, andbalancing means comprising at least one counterweight and associatedreversing means connected between the reciprocatory means and thecounterweight in such a manner that movement of the reciprocatory meansin either direction causes simultaneous movement of the counterweight inthe opposite direction, the apparatus being characterised in that saidreversing means comprises a pivoted rocker, first linking meansconnected at one end to the reciprocatory means and at the other to therocker, and second linking means connected at one end to thecounterweight and at the other end to the rocker, and wherein saidapparatus is symmetrical about a first plane which includes saidrectilinear axis, and is also symmetrical about a second plane which isat right angles to said first plane and also includes said rectilinearaxis.
 14. Apparatus according to claim 13, characterised in that thereis guide means operative to guide said counterweight for reciprocatorymovement along a rectilinear path.
 15. Apparatus according to claim 13,characterised in that said rocker is pivoted about an axis midwaybetween connections for said first and second linking means. 16.Apparatus according to claim 13, characterised in that the first andsecond linking means are mutually parallel and extend on the same sideof the rocker.
 17. Apparatus according to claim 12, characterised inthat the first linking means is equal in length to the second linkingmeans.
 18. Apparatus according to claim 13, characterised in that eachof the linking means is flexible and that each end of each of thelinking means is connected by a non-pivotal anchorage to saidreciprocatory means, said rocker or said counterweight, as the case maybe.
 19. Apparatus according to claim 18, characterised in that eachflexible linking means is constituted by a flexible blade.